Usually in text editors, during a block selection, moving first deselects the block, and moves the cursor to the end, or keeps it in place.
I guess back during Macintosh era, that behaviour was not standardized and moving left after a block selection would move the cursor.
That's one behavior that I will NOT replicate, perhaps it was a mistake on Apple's part, but I know it'll annoy me if the cursor shifts each time I go from a block selection to a position.